With the development of the wireless communication technology, there has been an explosive growth in demands for amount of traffic, amount of terminals and types of terminals in wireless network applications. The 5th Generation of mobile communication technology, also known as 5G, has become a trend of development for future networks. Machine Type Communication (MTC) has received more and more attention as one of the important application scenarios and techniques in 5G systems.
MTC, also referred to as Machine to Machine (M2M) communication, is currently a main form of application of Internet of Things (IoT). Currently available MTC devices are mainly based on Global System of Mobile communication (GSM) system. In the 3rd Generation Partnership Project (3GPP) Technical Report (TR) 45.820 V200, several techniques applicable to Comb-Internet of Things (C-IoT) have been disclosed, among which Narrow Band—Internet of Things (NB-IoT) is the most attractive one. The NB-IoT system has a system bandwidth of 200 kHz, which is the same as the channel bandwidth of the GSM system. This makes it very convenient for the NB-IoT system to reuse GSM spectrums and reduce interference with neighboring GSM channels. In the current Long Term Evolution (LTE) system, all uplink data is scheduled on a basis of Physical Resource Block (PRB). However, the uplink data in the NB-IoT is scheduled on a basis of sub-carrier. Therefore, the NB-IoT cannot reuse the uplink demodulation reference signal in the LTE system.